The invention relates to a lancet device for generating a puncture wound, in particular for withdrawing a body liquid for diagnostic purposes, and a lancet drive assembly for a lancet device.
In order to obtain a small quantity of body liquid (blood and/or interstitial liquid) from a part of the body (usually a finger or ear lobe) for analytical-diagnostic purposes, lancets are used that are stuck into the respective body part in order to generate a puncture wound. If this is effected manually, specially trained personnel are required for this purpose. Even then, puncturing is associated with considerable pain.
Blood withdrawal systems consisting of a lancet device and corresponding lancets that are specifically adapted to the corresponding lancet device have been in use for a long time. A housing of the lancet device contains a lancet drive by means of which a lancet is stuck mechanically into the skin. A spring serves as drive element for the puncturing motion. Initially very simple designs were customary, in which the lancet was directly attached to one end of a compression spring that was arranged in an elongated housing (e.g. U.S. Pat. No. 4,469,110).
However, blood withdrawal systems of this type failed to meet the difficult requirements that need to be satisfied when regular monitoring of analytical blood values is required. This applies in particular to diabetics who should control their blood sugar level frequently in order to be able to keep it within certain limits by injecting insulin. Extensive scientific investigations have shown that an intensive therapy scheme involving at least four blood analyses per day can achieve a dramatic reduction of extremely severe secondary damage caused by diabetes mellitus (for example retinopathy resulting in the patient going blind).
A prerequisite of this type of intensive therapy is that the withdrawal of blood be associated with as little pain as possible. A number of different blood withdrawal systems have been developed aiming for improvement in this regard.
Withdrawal of blood with little pain is made possible by lancet devices, whose lancet drive includes a drive rotor onto which acts, on the one hand, the drive spring on one side (drive side) such that the drive rotor can be put into a rotational motion about a rotation axis, and which, on the other hand, is coupled via a coupling mechanism (on the output side) to the lancet such that the rotation of the drive rotor resulting from the relaxation motion of the drive spring is transformed into a puncturing motion. The present invention relates to a lancet device with a rotor lancet drive of this type that is known in various embodiments.
Usually, the output-side coupling mechanism is designed such that the lancet is coupled to the drive rotor during the entire puncturing and returning motion (drive phase of the motion of the lancet drive) and thereby the lancet motion is completely controlled by the corresponding motion of the drive rotor. An early example of a design of this type is shown in U.S. Pat. No. 4,924,879. More modern embodiments are described, for example, in U.S. Pat. Nos. 6,409,740 and 6,419,661.
The known rotor lancet drives are usually tensioned by rotating the rotor backwards, against the force of the drive spring, by means of a suitable “drive side coupling mechanism.” More recently, a design has become known, in which an additional tensioning rotor is used for tensioning the drive spring. This allows the tensioning of the lancet drive to proceed in a tensioning phase of its motion by rotating the tensioning rotor in the same direction as the rotation of the drive rotor in the drive phase. This drive principle is also called OWADAC (one way alternating drive and cocking). A rotor drive of this type is described, for example, in EP 1384438 A1.
Despite extensive developmental work, there is still great interest in a lancet device that meets the, to some extent contradictory, requirements (minimal pain sensation, easy operability, compact design, cost-efficient construction) simultaneously and to the extent possible. A further requirement is that there should be no or as little as possible contamination of the lancet device during its use by exiting blood. It is an object of the invention to meet these requirements to the extent possible.